Disparities in Childhood CML Outcomes Persist Among Some European Countries and the US

Population-wide care ought to be optimal, regardless of region, argue the authors of a recent study.

In the era of tyrosine kinase inhibitors (TKIs), geographic disparities for survival among patients with childhood chronic myeloid leukemia (CML) persist, according to an analysis of registry data from Southern-Eastern European (SEE) countries and the US.1

The introduction of TKIs, particularly with the approval of imatinib in 2001, resulted in improved outcomes for patients with CML. The benefits of TKIs in the treatment of childhood CML, however, and “its effectiveness on the population level and about disparities in survival worldwide,” are not well understood, write the authors.1

The analysis includes cancer registry data from 1990 to 2014 from 12 SEE countries: Belarus, Bulgaria, Croatia, Cyprus, Greece, Malta, central Portugal, north Portugal, Romania-Cluj, northeast Romania, Serbia, Slovenia, Ukraine, and Turkey-Izmir. The authors include US data from the Surveillance Epidemiology and End Results (SEER) registry from 1990 to 2012; these data include demographic and clinical characteristics for children age 0 to 14 with CML, including acute lymphoblastic leukemia and acute myeloid leukemia.

The sample includes 427 children with a mean age at diagnosis of 8.6 years, 369 of whom are included in the survival analysis. The 2-year survival rate was 86% for children age 10 to 14, 80% for those age 5 to 9, and 58% for those younger than 5. Overall, survival increased by 23% after the introduction of TKIs. After multivariate proportional hazard pooled analysis that controlled for age, sex, and geographic area, there was a 67% lower risk of mortality after the introduction of TKIs.

Survival rates were 10% higher in the SEER registry compared with the SEE registries, and the risk of death was 56% greater in SEE countries, indicating that there is a survival disparity between the US and SEE countries. “Resource restrictions and suboptimal cancer health care organization across the SEE countries might have contributed to the less favorable outcome as compared to that in the USA,” write the authors.

The risk of death was also higher among younger children; the hazard ratio for children ages 0 to 4 was 2.71. The risk of death remained higher after the introduction of TKIs, suggesting that age of diagnosis is a prognostic indicator. Reasons for this difference, however, are not well understood. “Potential explanations may entail the presence of more aggressive disease-specific characteristics,” as well as higher risk for long-term adverse effects or other therapies, write the authors.

“The most immediate challenge is to offer optimal care at a population level in order to eliminate disparities in Europe and approach the favorable outcomes among children with CML in the USA,” the authors conclude.

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